A systemic immunoinformatics approach to design combinatorial multiepitope vaccine candidates against vector-borne bacterial infections exploiting the proteomes of the causative agent and vector for scrub typhus

An effective vaccine to prevent disease progression and transmission remains unavailable for most vector-borne bacterial infections. Recent comprehensive studies have explored not only the role of bacterial proteins in infection but also the significance of vector salivary proteins, underscoring the potential of combinatorial vaccines incorporating both bacterial and vector-derived antigens. Scrub typhus (ST), caused by the bacterium Orientia tsutsugamushi , is a mite-borne infection and a significant public health concern in eastern and southeastern Asia. Similar to other vector-borne bacterial diseases, the lack of an effective vaccine hampers prophylaxis against ST. Vaccine development is particularly challenging due to the extreme genetic diversity of major surface antigens, which limits cross-protection. In this study, a proteome-wide immunoinformatic approach was employed to identify immunodominant outer membrane proteins of O. tsutsugamushi , mapping conserved regions enriched in B-cell, Tc-cell, and Th-cell epitopes. Additionally, immunodominant regions from vector salivary proteins were identified. Using these segments, fifteen multi-epitope vaccines (MEVs) were designed and assessed for their physicochemical and immunological properties. The tertiary structure of the prioritized MEV was modelled, and its interactions with Toll-like receptors (TLR2, TLR4, and TLR5) were analyzed through molecular docking and molecular dynamics (MD) simulations. A glycosylation-deficient variant of the MEV was also designed and evaluated using the same methods. Immune simulations suggested that both MEVs could elicit a strong immune response. Furthermore, in silico cloning and expression analyses were conducted for bacterial expression system. While the proteome-wide combinatorial approach using immunodominant segments shows promise, experimental validation is necessary to confirm its efficacy against ST and other vector-borne bacterial infections. Strategy to configure a multiepitope vaccine for scrub typhus exploiting bacterial proteme and salivary proteome of the insect vector. • There is lack of an effective vaccine for Scrub typhus, a significant public health concern in eastern and southeastern Asia. • A strategy was adopted to identify immunodominant proteins and segments from bacterial proteome and salivary proteome of the insect vector. • 15 multiepitope vaccines (MEV) were configured by combining the immunodominant segments and evaluated to prioritize the most potent MEV. • Structural analysis and immune simulation highlighted prospect of the MEV to get translated in to an effective vaccine.